Symbol Symbol Name Meaning / definition Example ∠ angle formed by two rays ∠ABC = 30° measured angle ABC = 30° spherical angle AOB = 30° ∟ right angle = 90° α = 90° ° degree 1 turn = 360° α = 60° deg degree 1 turn = 360deg α = 60deg ′ prime arcminute, 1° = 60′ α = 60°59′ ″ double prime arcsecond, 1′ = 60″ α = 60°59′59″ line infinite line AB line segment line from point A to point B ray line that start from point A arc arc from point A to point B = 60° ⊥ perpendicular perpendicular lines (90° angle) AC ⊥ BC | | parallel parallel lines AB | | CD ≅ congruent to equivalence of geometric shapes and size ∆ABC≅ ∆XYZ ~ similarity same shapes, not same size ∆ABC~ ∆XYZ Δ triangle triangle shape ΔABC≅ ΔBCD |x–y| distance distance between points x and y | x–y | = 5 π pi constant π = 3.141592654… is the ratio between the circumference and diameter of a circle c = π·d = 2·π·r rad radians radians angle unit 360° = 2π rad c radians radians angle unit 360° = 2π c grad gradians / gons grads angle unit 360° = 400 grad g gradians / gons grads angle unit 360° = 400 g

### Emmanuel Abara Benson

I'm a highly-evolved 21st century human, a lover of knowledge and a Creative Writer amongst other things...